Micromirrors are key components of microelectromechanical system (MEMS)-based spatial light modulators (SLM). A typical MEMS-based SLM usually consists of an array of miniature micromirrors. These micromirrors are selectively deflected, for example, in response to an electrostatic force, which in turn selectively reflect incident light to produce digital images. Such micromirrors, however, are extremely sensitive to contamination, such as moisture and dust. This contamination has varying effects on the micromirrors, from capillary-condensation and post-release stiction to deterioration of the micromirror surfaces. Such effects can cause mechanical failure of the micromirrors in operation. For this and other reasons, micromirror array devices are often packaged after releasing.
Regardless of differences of the packaging methods currently developed for a micromirror array device, two substrates, one for supporting the device and another one for covering the device, and sealing medium(s) for bonding the two substrates are utilized. Most of the sealing mediums require application of heat during bonding. However, the heat, if not properly applied, may degrade the micromirror array device. For example, improperly applied heat may change the desired mechanical properties of the micromirrors. It may also thermally activate particles, such as impurities and particles making up the micromirrors, prompting diffusion of these activated particles within the micromirrors, thus exacerbating degradation of the micromirrors. Or heat may decrease anti-stiction materials within the package.
Therefore, a method and an apparatus are needed for packaging micromirror array devices.